Effect of field infestations of immature pigeonpea (Cajanus cajan (L.) Millsp.) pods on production of active (flight) and sedentary (flightless) morphs of Callosobruchus chinensis (L.)

A study conducted in Uganda on Callosobruchus chinensis showed that adults emerging from dry seed-infested and immature pod-infested pigeonpea differe d in a number of morphological and biological characteristics in one or bot h sexes. Adults emerging from dry seed-infested pigeonpea were more or less uniform in a number of these characteristics; in contrast, adults emerging from green pod-infested pigeonpea differed depending upon hen they emerged : the differences were greatest between those emerging during the 2nd to th e 6th days from first emergence, and those emerging from the 8th to the las t days of emergence. In one or both sexes, these differences were expressed in terms of elytral hue and size, body length, distance between the compou nd eyes, length of pygidium, body water content, pre-maturation periods, fe cundity and adult longevity. We suggest that these differences are due to p olymorphism, and specifically the predominance of flight forms among late e mergers from pod-infested pigeonpea. The differences observed in the two mo rphs of C. chinensis and ascribed to the flight and flightless forms, are t hought to be adaptations for survival and propagation under field and stora ge conditions, respectively. The predominance of emerged adults of the flig htless forms from dry seed and the flight forms from green pods were associ ated with low moisture content in dry seed and high moisture content in gre en pods, respectively. These observations show that bruchid control measure s are needed in the field as well as in storage. (C) 1999 Published by Else vier Science Ltd. All rights reserved.